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RE: Use of WOOD: Single Family Housing D

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This answer is simple, we design based upon ecconomic probablity. If you
recall storm drain design in college, it was explained that storm drain
systems are designed for a flood that occurs every "x" number of years. The
ecconomic model is done for a 50 year, 75 year and 100 year storm (for
examples). The risk is in the loss of life. What is an acceptable level to
design to. This is a question cities need to debate and answer - fore they
become responsible (in their own hearts) for the loss of lives when the
event occurs.
Structures follows the same guidelines. At what wind load do we design to or
what percentage of gravity in seismic events. The answer lies in the
frequency of the event. you may never experience the type of wind load you
are designing for, however since there are no guarantees in life, you may
yet experience the ultimate diseaster which proves out the engineers design.
If everything were overdesigned, the solution would hinder new construction
by making it unecconomical to construct buildings.

The exact answers to this question are what the evolution of our codes are
suppose to address with each new version. Unfortunately, sections such as
the Conventional Framing section do not follow this logic, but draw upon
industry lobby pressure to comprimise lesser standards.

The answer is one of ecconomics as to the level of design we strive to
attain - and it is a very fragile scale to work with.

As you indicated in your post, the solution is to revise prescriptive
measures so that they are not less than the minimum engineered solution.

Dennis Wish PE
-----Original Message-----
From: BD2PE(--nospam--at) [mailto:BD2PE(--nospam--at)]
Sent: Friday, August 21, 1998 8:31 PM
To: seaint(--nospam--at)
Subject: Re: Use of WOOD: Single Family Housing D


But why have they not been exposed to these design loads.

Do the wind pressures in the code truly correspond to the wind speeds.

If a building is designed for exposure C and is in an exposure B area, then
too will never see its design loads.

We have had design wind speeds in Reno and Tahoe exceeding the wind design
speed and have had only minor failures, mostly of architectural features,
it comes to wood framed structures.

I am not advocating that engineers are not important, but, in my opinion
are not needed in the consturcuction of the simple wood framed structure.